The current point to point protocol (PPP) provides a common standard for transporting multi-protocol datagrams over a point-to-point link. It provides the features of encapsulation, link configuration, maintenance, and authentication. PPP is used in many applications. In particular, the protocol has found significant usage for dial-up access to the Internet via the PSTN. The PPP protocol has been defined by the Internet Engineering Traffic Forum (IETF) and a general description of the protocol is given in ‘The point to point protocol, editor W. Simpson, July 1994, IETF RFC 1661’. A number of different datagram protocols or formats are provided for and these are allocated corresponding identifier numbers in IETF document RFC 1700, editor J. Reynolds, October 1994.
It will be appreciated that the different services that are supported by the PPP protocol have different quality of service (QoS) criteria. In current systems, this necessitates a separate channel with appropriate band width for each quality of service. This is wasteful in terms of traffic handling capacity, particularly where a single user has set up a multi-protocol PPP session and will need to occupy a number of channels.